A wide variety of systems including industrial systems, e-commerce systems, information systems, etc., employ packet-based communication networks. Examples of packet-based communication networks include networks that conform to Ethernet standards. The entities that communicate via a packet-based communication network may be referred to as nodes. Examples of nodes include computers, workstations, control devices, sensor devices, computational devices, information servers, etc.
The nodes in a packet-based communication network may be arranged as a set of subnets. Each subnet may provide communication among a corresponding subset of the nodes. Store-and-forward communication devices may be used to forward packets between the subnets. One example of a store-and-forward communication device is a router.
The nodes that communicate via a packet-based communication network may include local clocks. In addition, the nodes may synchronize the time values contained in their local clocks by exchanging timing packets via the packet-based communication network. For example, the nodes may implement the Precision Time Protocol (PTP) as set forth in the IEEE 1588 standard for synchronizing their local clocks by exchanging timing packets and determining the delay in timing packet transfer between nodes.
The amount of time taken by a store-and-forward communication device to forward timing packets between subnets may vary depending on the amount of other traffic underway. A variation in the time taken to forward timing packets between subnets usually causes variation in the delay of timing packet transfer between nodes. Unfortunately, a variable delay in timing packet transfer between nodes may hinder the accuracy of a time synchronization protocol such as PTP that relies on a determination of the delay in timing packet transfer.